A report by Pew Research last year showed that, as before, the majority of Americans (53 per cent) would be less likely to vote for a presidential candidate who doesn't believe in God. Unsurprisingly, this is higher among Republicans – 70 per cent of whom would be less likely to vote for an atheist, in comparison with 42 per cent of Democrats.
The message is clear: faith matters. So what do we know about the candidates who have launched their campaigns when it comes to their faith?
Ted Cruz (44): The Texas senator and Tea Party favourite was the first to throw his hat into the ring on March 23. A committed Southern Baptist, Cruz has been outspoken about religious freedom, both at home and abroad, and has taken a strong stance against same-sex marriage. He is currently seeking to introduce legislation to protect each state's right to make its own decision on the issue.
He was given a warm reception at last year's Values Voter Summit; the conference, hosted by the Family Research Council, is usually seen as an early indicator of conservative support for presidential candidates, and Cruz won the most support (25 per cent) in the poll at the end of the weekend.
Speaking of his personal faith in a 2013 interview with CBN News he said: "At the end of the day, faith is not organized religion; it's not going to a church. It is a personal relationship with Jesus Christ as your Lord and Saviour."
But although he rarely shies away from mixing his faith and politics, he said it was important for politicians "to avoid being a Pharisee, to avoid ostentatiously wrapping yourself in your faith, because I think in politics, it's too easy for that to become a crutch, for that to be politically useful."
His father, Pastor Rafael Cruz, is director of Purifying Fire Ministries – the ministry of Suzanne Hinn (wife of Benny). Cuban-born Pastor Cruz has compared Barack Obama's leadership approach to that of Fidel Castro, describing him as a Marxist who "seeks to destroy all concept of God".
Ted Cruz launched his campaign at Liberty University, Virginia, said to be the world's largest Christian university. It's safe to say he is gunning for the Christian vote. At the event he spoke of the "transformative love of Christ" that he has witnessed at work in his family, and kicked off his campaign with the rallying cry: "God's not done with America yet".
Rand Paul (52): An ophthalmologist, senator for Kentucky since 2011 and son of congressman and two-time presidential candidate Ron Paul. He was baptised into the Episcopal Church, but now attends a Presbyterian church, where his wife Kelley is a deacon.
"My faith has never been easy for me," Paul said at the 2012 Values Voter Summit, when he took the opportunity to outline his position on numerous issues from a faith perspective. He said his faith had "never been easy to talk about and never been without obstacles." Quoting Dostoyevsky, he said: "I did not arrive at my hosanna through childlike faith, but through a fiery furnace of doubt."
He continued: "I do not and cannot wear my religion on my sleeve. I am a Christian, but not always a good one. I am not completely free of doubts. I struggle to understand man's inhumanity to man," he said, adding that he also struggled with the personal tragedies he has encountered as a doctor.
In his confessional-style speech, he also said that he was "conflicted" about war, saying that good leaders only use force with great deliberation. "I'm not a pacifist, but I do think it unacceptable not to hate war," he said. "I don't think Jesus would have killed anyone, or condoned killing, perhaps not even in self-defence."
One issue he is clear about is abortion – he describes himself as "100 per cent pro-life". On gay marriage, he advocates for the decision to be made at state level. Personally, he opposes it, but said in a recent Fox News interview that he supports the idea of 'contracts' for gay couples with the legal rights of marriage – such as a civil union.
In a CBN video from a pastor's breakfast in March he said that there was a "moral crisis" in America, which has brought about the pressure for gay marriage. But people shouldn't necessarily look to Washington to be the answer, adding "We need a revival in the country. We need another Great Awakening with tent revivals of thousands of people saying reform or see what's going to happen if we don't reform."
Marco Rubio (43): The junior US senator from Florida launched his campaign on April 13 with a conference call to his biggest backers. The son of Cuban immigrants, his campaign is all about rescuing the American Dream – with a strong focus on the economy. At the 2013 Values Voter Summit he said: "If we're serious about saving the American Dream, we can't stop talking about [social issues]... We can't stop talking about them because the moral wellbeing of our people is directly linked to their economic wellbeing."
Rubio was born into a Catholic family and baptised into the church, attended a Mormon church for few years as a child (and was baptised again into the Mormon faith), but returned to the Catholic Church and took First Communion in 1984, according to a 2012 interview with Christianity Today.
He says in his 2013 memoir 'An American Son' that in the early 2000s his wife, Jeanette, started attending a Southern Baptist church with their children – Christ Fellowship in Miami. Rubio says the church "sparked a spiritual awakening in Jeanette's life, and eventually in mine, too".
But theologically he hadn't left the Catholic Church, he says, and in 2004 he felt called back. His four children have now also taken First Communion and they all attend Mass regularly, but the family still frequents Christ Fellowship and he gives generously to the church's ministry. He says the teaching at the evangelical church gave him a fresh appreciation for the meaning behind the tradition and liturgy in Catholicism.
Rubio also writes in his memoir of the importance of keeping faith in keeping personal ambition in check: "Our temporal ambitions are infinitely less important than our spiritual progress, but they are the stuff of life, too, and often beguiling, and they tempt us constantly to misplace our priorities... We all crave to make our mark in this life, and sometimes forget that our place in the next one matters more. I have been ambitious for worldly success. I hope I have been for the right reasons."
He upholds the teaching of the Catholic Church on gay marriage and abortion. In 2013 he co-sponsored a bill to ban abortions after 20 weeks, but allowed some exceptions, including in cases of rape and to protect the life of the mother. He thinks gay marriage legislation should be decided at a state-level, and was disappointed that the law on same-sex marriage in Florida was changed through the courts.
Ben Carson (63): The retired neurosurgeon is most renowned for his breakthrough work in separating conjoined twins. He was awarded the Presidential Medal of Freedom in 2008, he's written six books and has had a TV film made about his life.
Carson has been baptised twice into the Seventh Day Adventist Church, and writes in his 2008 book Gifted Hands that "The Adventist denomination is the only spiritual home I've ever known."
At his official campaign launch in his hometown of Detroit on May 4, which featured a gospel choir, he told the crowd: "I'm probably never going to be politically correct, because I'm not a politician. I don't want to be a politician because politicians do what is politically expedient, and I want to do what's right." Carson only joined the Republican Party in 2014.
His reputation for being outspoken, and at times controversial, has earned him the love of some conservatives – particularly after he slammed Obamacare at the National Prayer Breakfast.
He's critical of political correctness and defends the right to religious freedom. In his 2012 book America the Beautiful he writes: "Today the forces of political correctness would expel God from every public sphere in American life, and the hearts and minds of every man, woman, and child in America are up for grabs in this cataclysmic battle between the lovers of men and the lovers of God... I believe it is time for us to stand up and be counted."
He's also spoken widely of his pro-life stance and belief in 'traditional marriage'. In an op-ed for the Washington Times last year he wrote that "Attempting to characterize love and compassion for human life as a 'war on women' is deceitful and pathetic. We the people must stop allowing ourselves to be manipulated by those with agendas that do not include regard for the sanctity of life."
Speaking of his personal faith in an interview with CBN he said: "The most important thing for me is having a relationship with God. To know that the owner, the creator of the universe loves you, sent His Son to die for your sins, that's very empowering."
But although he appeals to the Christian vote in some respects, he isn't guaranteed support from Southern Baptists. Having been invited to speak at the Southern Baptist Pastors' Conference in June this year, he has now had to withdraw from the event after the conference president Willy Rice faced criticism for appearing to endorse a candidate, particularly one who was not a Southern Baptist, according to the Christian Examiner.
Carly Fiorina (60): Former CEO of Hewlett Packard, Fiorina worked for John McCain's presidential campaign in 2008 and in 2010 ran for Senate in California, though lost to her Democrat rival Barbara Boxer.
Fiorina was brought up in the Episcopal Church, describes herself as a Christian and chairs the board of faith-based microfinance charity Operation International. Although she is not known to be a regular churchgoer, she said in an interview with CBN News that her faith had helped her get through personal difficulties, including the death of her step-daughter Lori Ann in 2009, and her own battle with breast cancer which was diagnosed the same year.
"I am quite certain, that I would not have been able to endure those without a personal relationship with Jesus Christ," she said. "I am forever grateful that I rediscovered a personal relationship with God before that happened."
She told the Christian Post earlier this year her Christian faith means that "I believe that everyone of us is equal in the eyes of God, and therefore, I know that everyone is capable of living a life of dignity, purpose, and meaning."
Fiorina opposes abortion, except in cases of rape, incest and when the mother's life is at risk. In an interview with Breitbart News the day before she announced her candidacy she said her opinion had been shaped by personal experience – having accompanied her best friend to have an abortion. "I watched how she was dealt with at that abortion clinic, the fact that she really wasn't presented with any options... One of the things that struck me as so sad is, she was never really encouraged to even evaluate that choice," Fiorina said.
On marriage she says that same-sex couples should be allowed civil unions and the same benefits as those who are married, but believes that marriage is between a man and a woman. At an event in Iowa in April she described marriage as a "spiritual institution".
Mike Huckabee (59): The former Republican governor of Arkansas and ordained Southern Baptist minister also ran in the 2008 presidential election and won eight primaries, but his campaign faltered partly from lack of funds. Huckabee hosted an eponymous television show on Fox News Channel for six years, until January, and still hosts 'The Huckabee Report' on ABC Radio.
He was raised Southern Baptist, and gave his first sermon as a teenager. Speaking of the importance of personal faith he said recently: "In every person's life the only thing that makes life truly worth living the next day is knowing that that emptiness is filled by the Lord Jesus Christ." After his first degree in religion, Huckabee attended Southwestern Baptist Theological Seminary but didn't finish his master's degree. He worked as a pastor in Arkansas for 12 years, and still plays the bass guitar in the church band.
In a 2007 interview with the Religion News Service, he said he thought his pastoral experience was good preparation for his political work. "I think it's the greatest preparation that a person can have for public service," he said. "There's not any social pathology that I couldn't put a name and a face to... I've dealt with a 14-year-old girl who's pregnant and hasn't told her parents yet. I've talked to the young couple who's head over heels in debt... I think it gives you a real perspective about people and what they're going through that's important."
He is concerned about the place of Christianity in contemporary America, and has been highly critical of the opposition to religious liberty laws in Arkansas and Indiana. Speaking on the Family Research Council's 'Washington Watch' Huckabee said: "It won't stop, until there are no more churches, until there are no more people who are spreading the gospel, and I'm talking now about the unabridged, unapologetic gospel that is really God's truth."
Huckabee is staunchly opposed to abortion, even in cases of rape and incest and has called for Roe v Wade to be repealed. He's also a committed defender of traditional marriage, and has signed a pledge in opposition to the current case in the Supreme Court. In his 2015 book God, Guns, Grits, and Gravy he writes: "For believers, changing the definition of marriage is no more an option than it would be for observant Jews to serve bacon-wrapped shrimp or Hindus to open a steakhouse." In the past he has also opposed civil unions for same-sex couples.
In his campaign launch video Huckabee vows to lead with "moral clarity". "There's a difference between right and wrong, there's a difference between good and evil," he says, adding that he will "keep all the options on the table in order to defeat the evil forces of radical Islam."
Rick Santorum (57): The former US senator for Pennsylvania is standing as a candidate for a second time, having finished second in the Republican nominations in 2012.
Santorum was raised a Catholic but has become more devout and conservative over the past couple of decades. He and his wife Karen recommitted themselves to the faith before they got married, and they are now known for their strong commitment to family values. In 2005 he published It Takes a Family: Conservatism and the Common Good, in which he argued that liberal social policies have undermined the place of the family in society.
Santorum and his family have attended St Catherine of Siena Church in Great Falls, Virginia for many years. During the last presidential campaign Santorum still tried to attend Mass every day whenever possible, according to an article in the New Republic.
They have home schooled their younger children, something he has said in the past that he would continue if he made it to the White House. His older boys went to a private school in Washington DC affiliated with Opus Dei, a lay movement that emphasises holiness in everyday life.
Santorum is CEO of EchoLight Studios, a faith-based film studio and distributor. Speaking of his decision to get involved the Christian film industry, he told Christian Today last year: "If we want to impact the political system and shape the country, then we have to reclaim the public square and make an impact in popular culture."
He's opposed to same-sex marriage, and is among a number of prominent Christian leaders who have signed the Defend Marriage Pledge directed at the Supreme Court Justices. He has said it would be a "violation of my faith" to attend a same-sex wedding. He is also outspoken against abortion, and has said it should be illegal, even in cases of rape and incest, although not when the mother's life is in danger.
In February this year he and Karen published Bella's Gift, telling the story of their youngest daughter Isabella, who has a rare genetic condition and wasn't expected to see her first birthday. Bella is now seven – something he credits to the grace of God.
In the book they write: "We thank God every day for Bella. She has taught us that hope in Christ brings joy... Through Bella, God gives us the grace to cooperate with His will and empty ourselves for others. Then we can become His arms, embracing the world; His legs, still walking dusty streets; and His heart, still beating with the Divine Compassion manifested in Jesus Christ, the One who became the leas of these in order to bring all of us into the full communion of Love."
George Pataki (69): The former three-term governor of New York is generally considered a bit of a long shot for the Republican nomination, but he nonetheless threw his hat into the ring on May 28. Has been out of politics and working as a lawyer and businessman for the past eight years.
He was brought up Roman Catholic, but hasn't advertised his religious credentials, possibly because of his progressive stance on a number of key issues – he is pro-gay marriage and pro-choice. He has criticised fellow Republicans for getting hung up on social issues and said in a New Hampshire advert which launched in April: "Defeating Islamic terrorists, shrinking government, growing the economy – these are the issues that matter most, instead we're debating social issues like abortion and gay rights."
Unlike many other Republican candidates he was also critical of Indiana's religious freedom law, describing it as discriminatory. "There is no place for discrimination in America," he said. "We have travelled too far together to be debating a law that allows people to be discriminated against on the basis of sexual orientation."
According to a 2003 article in the New York Post, he allegedly considered joining the Freemasons but decided it went against his Catholic faith.
His wife, Libby, co-founded One Jerusalem, an organisation "dedicated to the preservation of Israel as a Jewish state" and Pataki has spoken of his close ties to the Jewish community when he was growing up in New York.
Lindsey Graham (59): The Republican US Senator from South Carolina and former Air Force colonel announced his candidacy on June 1. He's a Southern Baptist and attends Corinth Baptist Church in Seneca, SC.
He's accused by some of being too liberal, possibly because of his outspoken opposition to the Tea Party. While he is against same-sex marriage on principle, he has also said it may be time to accept that society is changing.
In 2008 he supported a constitutional amendment to ban gay marriage, but in an interview with Boston Herald Radio last month he said: "Am I for traditional marriage? Yes, I believe marriage has stood the test of time between a man and a woman, ordained by God, and that's — most societies have been organized around that concept." He added: "Things are changing, so at the end of the day, being for traditional marriage without animosity is where I stand. If the Supreme Court rules sometime this year that same-sex marriage bans are unconstitutional, then that will be a defining moment in that debate. And it will be time for us to move forward as a society."
In the same interview he told social conservatives to "hold your head up high". He added that he was "a pro-life guy" apart from in cases of rape and incest. "When a woman is raped, it is not the will of God, it is a crime," Graham said. Responding to a question about some of rhetoric used by Christian Republicans around social issues he said: "At the end of the day we want to showcase as Christian conservatives a loving heart."
In an appearance on a local ABC news station he said that legislating on religious freedom was a "very complicated endeavour for a democracy" pointing to the importance of defending the rights and liberties of all. "The one thing I will not tolerate is a national religion, even though I am a Christian, because that is counter to what we are as a people... The strength of this nation is that people can worship God on their own terms... We don't need to drive God out of the public square, we just need to make sure we've got the right balance."
His stance on foreign policy and national defence is a key campaign issue, with the campaign slogan "security through strength", particularly drawing on his experience in the armed forces. He calls for a stronger approach to radical Islam, saying: "We must fight them over there to keep them from coming here."
He has also championed religious freedom abroad, and in an interview with Tony Perkins of the Family Research Council he criticised President Obama for failing to recognise events in the Middle East as a religious war. He compared the actions of Islamic State in trying to create a "master religion for the world" to Hitler's attempt to create a master race. "We've got to come to the aid of our Christian brothers and sisters, to Muslims who are being killed because they won't agree with these guys, to the Yazidis, to just anybody that gets in their way."
Rick Perry (65): The four-term governor of Texas announced his second presidential run on June 4. Perry grew up on a street with a Methodist church at one end and a Baptist church at the other, regularly attending both, though his family were members of the United Methodist Church.
In more recent years he has shifted from the Methodist tradition and in 2007 began attending Lake Hills Church, a large evangelical congregation in Austin, Texas. Last year he was re-baptised in a private ceremony in a river in Texas.
Speaking to students at Liberty University in 2011 about his personal faith, he said: "My faith journey is not the story of someone who turned to God because I wanted to. It was because I had nowhere else to turn. I spent many a night pondering my purpose, talking to God, wondering what to do with this one life among the billions that were on the planet. What I learned as I wrestled with God is that I didn't have to have all the answers, that they would be revealed to me in due time and that I needed to trust him."
He also speaks of his political career as a calling from God. During his 2012 presidential campaign, he said: "I'd been called to the ministry. I've just always been really stunned by how big a pulpit I was going to have. I truly believe with all my heart that God has put me in this place at this time to do his will."
He believes abortion should only be legal in cases of rape, incest or when the mother's life is at risk, and in 2013 signed a bill in Texas to reduce the abortion limit to 20 weeks. Perry is also against gay marriage and introduced a constitutional amendment in Texas in 2005 to define marriage as being between a man and a women, which was supported by 76 per cent of voters.
Like a number of the Republican candidates he also argues for stronger action on tackling radical Islam, and ISIS in particular. "[Obama] says that ISIS is [not] a religious movement – again he's simply wrong," he said in a speech in February this year. "To deny the fundamental religious nature of the threat and to downplay the seriousness of it is naive, it is dangerous, and it is misguided. ISIS represents the worst threat to freedom since communism."
Jeb Bush (62): The former governor of Florida is certainly among the more well-known candidates in the crowded Republican field.
Bush was raised in the Episcopal Church, but converted to his wife Columba's Catholic faith in 1994. In a speech in Italy in 2009 he said (according to the New York Times): "I love the sacraments of the Catholic Church, the timeless nature of the message of the Catholic Church, the fact that the catholic Church believes in, and acts on, absolute truth as its foundational principle and doesn't move with the tides of modern times, as my former religion did." He described his conversion as "one of the most important times of my life" when speaking at the National Hispanic Christian Leadership Conference earlier this year.
This was one of a number of speeches to Christian audiences in recent months in which he has addressed the need to protect the right to religious liberty and Christian conscience. "There's no more powerful or liberating influence on this earth than the Christian conscience in action. And today in America it is important to respect and protect Christians acting on their faith," he told the audience of Latino pastors.
Speaking at Liberty University's commencement in May he said that although some may think that Christianity is "static, narrow, and outdated," Christians can choose how they respond. "We can take this as unfair criticism, as it typically is, or we can take it as further challenge to show in our lives the most dynamic, inclusive, and joyful message that ever came into the world."
He has described his personal faith as "the architecture that gives me the serenity I need, not just as a public leader or in life. It gives me peace. It allows me to have a closer relationship with my creator." Bush attends the Church of the Little Flower in Coral Gables, Florida with his family. In 2006 he said that he carries rosary beads around in his pocket, saying that "it gives me comfort".
In keeping with Catholic beliefs Bush is pro-life and promoted a ban on late term abortions while he was governor. But he differs from the Church in his view on capital punishment; during his term (1999-2007) the state executed 21 people, more than under any of the three previous governors after the death penalty was reintroduced in 1976.
He told CBN's The Brody File last month that he shared Christian conservatives' concerns about same-sex marriage and doesn't think there should be a constitutional right for same-sex marriage, adding that "we need to be stalwart supporters of traditional marriage."
Speaking more generally about the state of American morality he said: "I don't think that we can impose a spiritual awakening from Washington DC by passing a law... but we have the crumbling of our moral foundation of our country that is quite disturbing."
Donald Trump (69): The business mogul and reality TV star launched his campaign on June 16 and in his speech declared his $8.7 billion net worth as well as promising to be "the greatest jobs president that God ever created".
Trump is a Presbyterian "and proud of it", despite numerous reports that he is Catholic or a member of the Dutch Reformed Church. In a 2011 interview with CBN's The Brody File when he was considering making a 2012 presidential bid, he said: "I believe in God. I am Christian. I think the Bible is certainly, it is THE book. It is the thing."
And he's so concerned about the Bible that he daren't throw away any of the ones that he is given. (He gets sent a lot.) "There's no way I would ever throw anything, to do anything negative to a Bible... I would have a fear of doing something other than very positive so actually I store them and keep them and sometimes give them away to other people."
He said he used to attend First Presbyterian Church in Jamaica, Queens, and now goes to church "as much as I can. Always on Christmas. Always on Easter. Always when there's a major occasion. And during the Sundays. I'm a Sunday church person."
His political allegiance has changed numerous times over the year and he has contributed financially to both Republican and Democrat campaigns over the years. He was listed on the Reform Party primary ballot in 1999, joined the Democrats in 2001, was registered an independent in 2011, before settling with the GOP again in 2012.
Even so, he emphasises his commitment to conservative values. In 2013 he said his views on gay marriage are changing but he remains in favour of traditional marriage. "I think I'm evolving, and I think I'm a very fair person, but I have been for traditional marriage. I am for traditional marriage, I am for a marriage between a man and a woman." Trump has also said that he is now pro-life, partly as a result of seeing friends who were going to abort a pregnancy but decided to keep the child.
In an interview with CBN news he said that he thinks Christians are discriminated against in US immigration. "If you're a Christian living in Syria, you can't come into this country, and yet if you're a Muslim living in Syria, who are not under attack, they can come in... If you're from Europe and a Muslim you can come in, but if you're from Europe and a Christian you can't come in... The Christians are being treated horribly because we have nobody to represent the Christians. Believe me... if I win I will be the greatest representative of the Christians that they have had in a long time."
Bobby Jindal (44): The second-term governor of Louisiana is the youngest candidate seeking the Republican nomination and currently sits at the bottom of the 15-person list in the polls.
Jindal converted to Catholicism from his family's Hindu faith after exploring Christianity at high school and was baptised when he was at Brown University. His wife, Surpriya also converted from Hinduism. Jindal has spoken widely about his conversion, which he describes as a gradual process over a two-year period.
His parents moved to Louisiana from India a few months before he was born and he says his first experience of Christianity as a child wasn't exactly positive – a Southern Baptist friend told him: "you and your parents are going to hell".
A more positive and influential moment in his conversion story was being give a Bible by a high school friend as a Christmas present. "I cannot begin to describe my feelings when I first read the New Testament texts. I saw myself in many of the parables and felt as if the Bible had been written especially for me," he wrote. The actual moment of his conversion came some time later when he saw a film about the crucifixion that was screened in the Louisiana State University chapel. "God chose that moment to hit me harder than I've ever been hit before," he told a Louisiana prayer rally in January, according to the Guardian.
His parents were angered by his decision and stopped supporting him financially. "My parents have never truly accepted my conversion and still see my faith as a negative that overshadows my accomplishments," he wrote.
Jindal describes himself as an "evangelical Catholic". In his campaign launch speech he said: "I know that some think that I talk about my faith too much, but I will not be silenced... They don't seem to accept the idea that you can be both intellectual and Christian." As a slightly different take on the launch video, he posted footage of him telling his three kids that he was running for president.
His opposition to abortion stance has some interesting roots. When speaking about points on the journey of his conversion, he said he met a "pretty girl" at school who said she wanted to become a Supreme Court justice in order to overturn Roe v Wade and he said he was inspired by her sense of conviction.
He also opposes gay marriage, and wanted to introduce a 'Marriage and Conscience Act' in Louisiana to prevent businesses from being discriminated against for refusing gay customers on religious grounds. Although this was defeated by the state legislature, he then signed an executive order seeking to protect those rights. He has spoken passionately about religious freedom, saying at a prayer event in May: "The United States of America did not create religious liberty, religious liberty created the United States of America."
At the prayer rally in Louisiana, Jindal said spiritual revival was the answer to America's problems: "We can't just elect a candidate to fix what ails our country. We can't just pass a law to fix what ails our country. We need a spiritual revival to fix what ails our country."
Chris Christie (52): The governor of New Jersey launched his presidential bid at his high school in Livingston, New Jersey on June 30. Once considered a frontrunner, the 'Bridgegate' scandal and economic troubles in his home state have damaged his reputation, though not counted him out of the race entirely.
Christie was brought up in the Catholic faith, and attends Mass with his family at St Joseph's in Mendham, New Jersey, where his wife Mary Pat led Sunday school for many years, according to WNYC. He went to a Catholic University, Seton Hall, and his children go to Catholic schools. He counts the Archbishop of Newark as a friend.
But he doesn't follow the teaching of the Catholic Church on all issues. One issue where he diverges from Church is homosexuality. In an interview with Piers Morgan in 2011 he said: "My religion says it's a sin. But for me, I have always believed that people are born with the predisposition to be homosexual. And so I think if someone is born that way it's very difficult to say then that that's a sin. I understand that my church says that. But for me personally, I don't look upon someone who's homosexual as a sinner."
He supports civil unions for same-sex couples but is not in favour of gay marriage. "I believe marriage is an institution between one man and woman. I think it's special and unique in society... but I am in favour of making sure that homosexual couples have the same legal rights as heterosexual couples," he told Morgan. Speaking after the Supreme Court's decision to uphold gay marriage, he said he didn't agree with the decision, because each state should have been able to decide. But unlike some, he has said that people should comply with the law.
Christie is pro-life, apart from exceptional cases of rape, incest and to protect the life of the mother. He has said that he was pro-choice before going for the pre-natal scan of his daughter (who is now 19) and hearing the baby's heartbeat. Although he has said that he sees religion as "a personal thing" he said at a Catholic Conference last year that his faith is a "huge part" of his life and "At every stage of life our faith is there to help guide us... While I admire and absolutely support the diversity in our state, I am who I am."
Scott Walker (47): The second-term governor of Wisconsin is the son of a Baptist preacher and the only presidential candidate without a college degree, as he dropped out of Marquette University after three years.
Walker remained a Baptist as an adult, and was a deacon at Underwood Memorial Baptist Church in Wauwatosa, Wisconsin, until 2005. At that time the family moved to Meadowbrook, a non-denominational evangelical church. It appears that they decided to leave Underwood because it had moved in a more liberal direction, although Walker said it was primarily for their two children. He has spoken a number of times about the significance of his morning devotionals and thanked his supporters for praying for him.
"My relationship with God drives every major decision in my life" he said in a statement to the New York Times. Speaking at a breakfast for Christian businessmen in 2009 (before he became governor), he reflected on the importance of the hymn 'Trust and Obey' in his faith journey. A key moment was deciding for himself to follow Christ at the age of 13: "Before that it was kind of like following the rules, but just because that's the right thing to do, this is saying I have just...said I am going to trust in you, Christ, to tell me where to go and to the best of my ability I'm going to obey where you lead me. And that has made all the difference in the world to me. Through good times and bad." Consequently, he believes God told him who he should marry and when he should run for governor.
On how his faith and politics relate, he said in an interview with the Christian Post: "There's not a play card, if you will, that tells me how to vote or how to act on certain issues. So, it's not like issue by issue it drives me. But, the larger context, not only the policy decisions I make, but how I make them, how I interact with people, how I treat people. All of those things are, without a doubt, driven by my faith."
His experience as governor hasn't been entirely straightforward. His opposition to collective bargaining rights for public sector workers in his state led to huge protests and a recall election in 2012, which he won. Speaking before the June 2012 election in an interview with CBN's 'The Brody File' he said: "We realize that all this is just a temporary thing and God's got a plan for us that, who knows where it might be, beyond just serving as governor of this state, but if we stay true to that, there's always comfort...God's grace is always abundant no matter what you do."
Since the decision of the Supreme Court to legalise gay marriage, Walker has called for a constitutional amendment to allow states to define marriage and "protect the institution of marriage". He is also pro-life and has recently supported a bill to reduce the abortion limit in Wisconsin to 20 weeks, without any exceptions for the victims of rape or incest.
He has emphasised his commitment to tackling radical Islamic terrorism and working on building a more positive relationship with Israel.
John Kasich (63): The Republican Governor of Ohio has worked as chairman of the House Budget Committee, written three books and as a presenter on Fox.
Kasich was raised in a Roman Catholic home and fell away from faith as an adult, but returned and converted to Anglicanism after personal tragedy made him question the existence of God. Together with his wife, Karen, he now worships at St Augustine's Anglican Church, in Westerville, Ohio.
In 1987, Kasich's parents were killed in a car crash by a drunk driver. Prompted by a church minister, he was drawn to think about whether God existed and if he did whether he could have a relationship with him. He invited a group of friends to join him in his exploration of faith. They have now been holding a fortnightly Bible study group for more than 20 years, and the group became the subject of his 2010 book Every Other Monday: Twenty years of life, lunch, faith and friendship. He describes the group as "guys trying to make their way through life". "We spend so much time studying the sports section and working on our jobs, how many of us really spend time to think about the biggest issues in life?" he told Fox news.
He was running for governor when the book came out and was asked whether he thought it was God's will for him to win. Kasich said: "I think what God wants out of this is for me to be a better man. I have no clue as to whether He thinks it's important if I win or not."
Reiterating his sense of balance between the eternal and the temporal, he said at this year's Faith and Freedom Coalition Conference: "I have a mission, and I have a role on this earth. But I am trying to prepare myself for the world that's yet to come."
Controversially, he has defended Obamacare, and in doing so repeatedly cited Matthew 25 – Jesus' instruction to care for "the least of these". In an interview with the National Journal he praised Pope Francis for his emphasis on caring for the poor. He said: "The Pope's not saying, 'Let's just abandon everything up until now.' He's saying, 'But wait a minute! Before we get to the rules, let's look at the good stuff. Let's have the dessert first!' ... So instead of getting into the judgment, why don't we get into the feeding the hungry and clothing the naked and helping the imprisoned and helping the lonely? That's what we're commanded to do."
Kasich does not support same-sex marriage, but although some of the other Republican candidates have called for opposition to the Supreme Court's ruling, he has said Christians should abide by it. He is pro-life, except in cases of rape and incest.
Kasich has been criticised for speaking about his faith so much, and particularly for referencing the Bible to support policy – something he defended by saying it was so people knew what his ideas were based on. In an interview with The Columbus Dispatch he said: "My faith is part of me. In terms of how it affects my public policy ... on my best days, I sort of have an eternal perspective, which is really a great thing to have, because it frees you up. You don't get caught up in some of the things that can get in your way when you make decisions."
Hillary Clinton (67): Clinton is the most well-known of the candidates (and expected candidates), as a former secretary of state, senator and first lady. She grew up in the Methodist Church, admits to praying regularly and reading and studying the Bible, and used to teach Sunday school. She often attends Foundry United Methodist Church in Washington and says her faith spurred into wanting to take an active role in the world.
In a 2007 interview with the New York Times she described her faith as being like "background music". "It's there all the time," she said. "It's not something you have to think about, you believe it. You have a faith centre out of which the rest flows."
She also said she recognised that she "had to believe with both my head and my heart if it [faith] was going to sustain me over time".
In the same interview she was asked whether she believes in the resurrection (she does), and whether faith in Jesus was necessary to get to heaven – something which she's "a little more open to". She acknowledged that it's something she's often asked theologians, adding that there are many who feel "who are we to read God's mind about such a weighty decision as that".
Clinton supports family planning, and the idea of safe, legal abortion. She has said in the past that she wants to bring down the abortion rate, but keep it legal – which seems to align her with the position under the Clinton administration which was "safe, legal and rare".
Before 2013 she was publicly opposed to gay marriage (although in favour of same-sex civil unions), something which is expected to pose a problem for her among liberals. Defending her change in position on the issue, she said in an interview last year: "One of my big problems right now is that too many people believe they have a direct line to the divine and they never want to change their mind about anything."
Going a step further, a spokesperson announced four days into her campaign: "Hillary Clinton supports marriage equality and hopes the Supreme Court will come down on the side of same-sex couples being guaranteed that constitutional right."
Bernie Sanders (73): The independent junior US senator from Vermont announced he was running for president in a news release on April 29. He is probably the least openly religious and most left-wing presidential candidate. He caucuses with the Democrats in the Senate but has never joined the party and is the longest serving independent member of Congress in American history.
Sanders is Jewish by birth but says he is not now involved in organised religion. After graduating from college he spent some time on a kibbutz in Israel. His father's family emigrated from Poland, and many of his father's relatives were killed in the Holocaust.
A self-described democratic socialist with a concern for growing income inequality, Sanders has expressed deep admiration for Pope Francis, and said "I find myself very close to [his] teachings". He also described the Pope as "incredibly smart and brave", according to USA Today.
Sanders is pro-choice and supports gay marriage. He talks about the need for a "political revolution" – changing the agenda from personality politics and the dominance of the top one per cent to making America work for the majority. And while there's much about the political scene that he doesn't like, ultimately if he believes in anything it's in the power of politics to make a difference.
In an interview with The Nation, he said: "when I talk about a political revolution, what I am referring to is the need to do more than just win the next election. It's about creating a situation where we are involving millions of people in the process who are not now involved, and changing the nature of media so they are talking about issues that reflect the needs and the pains that so many of our people are currently feeling."
Martin O'Malley (52): The former governor of Maryland (2007-2015) announced his candidacy on May 30. O'Malley was brought up Catholic and had a very Catholic education, attending a Catholic elementary school, a Jesuit high school and then studying at the Catholic University of America in Washington DC.
In a 2002 speech to students at his old high school, he said (according to the Daily Beast) his Catholic education underpinned his passion for politics, particularly his emphasis on human dignity. "I learned... to search for Christ in the faces of others including, and especially, the faces of the poor... I learned... to recognize and confront the enemy within – the original sin of our own culture and environment that would have us think less of people who – because of race, or class, or place – are not like us ... And I learned that it is not enough to have faith, you must also have the courage to risk action on that faith, to risk failure upon that faith: the faith that one person can make a difference and that each of us must try."
He regularly attends St Francis of Assisi Church in Baltimore and although he is described as devout, he goes against the Church's position on a number of social issues. He is pro-choice, supports same-sex marriage, and sponsored the law to legalise gay marriage in Maryland. Explaining his stance on this issue in relation to his faith, he said: "I've found that the passage of marriage equality actually squares with the most important social teachings of my faith, which is to believe in the dignity of every person and to believe in our own responsibility to advance the common good. Part of that advancement means changing laws when they are unjust, when they are not applied equally to all people."
He also disagreed with US Catholic bishops over requirements that employers provide contraception within their health care provision. In an interview with CNN, he said: "I am Catholic. And I think... there's been a little bit too much hyperventilating over this issue... This is not about abortion, it's about covering contraception as part of the health care coverage – mandatory basic coverage," he said. "These same rules apply in countries like Italy, which have overwhelming numbers of Catholics, and yet we did not see the reaction in those countries to these sorts of things."
One issue where he is aligned with the Catholic Church is capital punishment; in 2013 he signed a Bill that repealed the death penalty for all future convictions in Maryland. And he's also been vocal about the need for immigration reform, responding to the crisis of unaccompanied minors entering the US illegally by offering refuge to more than 2,000 children in Maryland. In an impassioned speech last year he said: "It is contrary to everything we stand for to try to summarily send children back to death," adding that "Through all of the great world religions we are told that hospitality to strangers is an essential human dignity."
Lincoln Chafee (62): The former Governor of Rhode Island who was a Republican, then an Independent and is now a Democrat, officially launched his longshot campaign on June 3.
He was raised in the Episcopalian Church though tends not to discuss religion or his personal faith much in interviews. He believes in a strict separation of church and state and promotes religious tolerance. In 2010 he said: "Religious tolerance should not become a victim of popular or political passions."
But his fervour for tolerance proved problematic in 2011 when he insisted on calling the Christmas tree in the Rhode Island State House a 'holiday tree', prompting thousands of complaints and a fair amount of national uproar. Chafee explained: "If it's in my house it's a Christmas tree, but when I'm representing all of Rhode Island I have to be respectful of everyone."
He is pro-choice and has argued for it to remain a federal decision to protect the rights of poor women. He is also a long-time supporter of same-sex marriage, and in 2013 signed gay marriage into law in Rhode Island. At the time he wrote in the New York Times: "Much of the argument for and against gay marriage has revolved around the morality of the issue. Each side feels intensely that its position is more righteous that the other side's. I personally feel that Rhode Island is a better state, and America is a better country, when we are as inclusive as possible."
His campaign launch video refers to his reputation for being a "peacemaker" and "speaking truth to power". He has made the fact that he was the only Republican Senator to vote against the Iraq war in 2002 a central issue of the campaign, using it to distinguish himself from Hillary Clinton, who voted in favour.
Jim Webb (69): A Vietnam war veteran, journalist and author, Webb served as US Senator from Virginia between 2007 and 2013, and was Secretary of the Navy from 1987 to 1988.
He is described as a non-denominational Christian. In a lengthy blog post that announced his candidacy on July 2, Webb said: "outside my faith and my family, my greatest love will always be for this amazing country".
Webb was a strong opponent of the Iraq war (for strategic reasons rather than humanitarian concerns), though his son served in the war.
He has been consistently pro-choice. He was against same-sex marriage while he was senator but seems to have changed his mind. Last October he said in an interview with NBC that he thought that the nation's evolution on the issue was "a really good thing for this country".
He responded to the Supreme Court's decision by saying that it was "an historically significant historical application of the 14th Amendment, ensuring that our government no longer discriminates but also more clearly defining the separation of church and state. The decision provides religious groups 'proper protection' under the First Amendment to 'continue to advocate' their beliefs regarding traditional marriage."